Edexcel Jun 2011 Paper 5 Q14 (with explained solutions) |

Skip to content

Edexcel Jun 2011 Paper 5 Q14

Answers available below

PMT 14 This question is about synthetically produced painkillers and anaesthetics. (a) The local anaesthetic procaine can be synthesised from benzoic acid. The simplified route is shown below. COOH COOH COCl step 1 benzoic acid NO2 step 2 PCl5 heat under reflux NO2 step 3 COOCH2CH2N(C2H5)2 COOCH2CH2N(C2H5)2 step 4 NH2 procaine NO2 (i) Suggest the two reagents needed for step 1. (2)12 *P38480A01224*<br />
(ii) Draw the apparatus needed to heat under reflux in step 2. (iii) Suggest why the reagents for the reaction in step 2 are PMT (3) (2) heatedunder reflux(iv) Give the structural formula for the organic reagent needed in step 3. (v) What type of reaction is taking place in step 4? Suggest the reagents used. (1) (2)*P38480A01324* 13 Turn over<br />
PMT (b) A student produced a sample of aspirin by the esterification of 9.40 g of 2-hydroxybenzoic acid with excess ethanoic anhydride. OH H3C OH + (CH3CO)2O OH + CH3COOH 2-hydroxybenzoic acid ethanoic anhydride aspirin After purification by recrystallization, 7.77 g of aspirin was obtained. [Mr of 2-hydroxybenzoic acid = 138, Mr of aspirin = 180] (i) Calculate the percentage yield obtained. *(ii) Outline how to purify a solid, such as aspirin, by recrystallization, using water as the solvent. (3) (4)14 *P38480A01424*<br />
PMT (iii) Explain what effect recrystallization has on the final yield. (1)(c) Paracetamol is found in many non-prescription painkillers, often in conjunction with other compounds such as codeine. OH NHCOCH3 paracetamol (i) Suggest, by name or formula, a reagent that could be used to form paracetamol from 4-aminophenol. (ii) Suggest why sales of non-prescription painkillers, often containing paracetamol and codeine, are limited to 32 tablets. (1) (1)(iii) Explain why paracetamol is only slightly soluble in water although it can form hydrogen bonds with water. (1)(Total for Question 14 = 21 marks) *P38480A01524* 15 Turn over<br />

Show answer

Reject Mark Acceptable Answers Conc. Nitric acid (1) Conc. Sulfuric acid (1) Allow correct formulae Ignore state symbols Sulfuric acid and nitric acid with no mention of concentrated scores (1) Acceptable Answers Reject Mark Mark Conical flask in diagram or label Pear shaped/round bottomed flask & heat source (1) Allow vertical arrow with or without the word heat Allow water bath as a heat source Liebig condenser, shown vertically (1) (Water) flow shown correctly into a jacket (1) Ignore thermometers unless stoppered Penalise (one for each): Stopper/sealed Gaps between flask and condenser Condenser inner tube extends into liquid in flask Acceptable Answers Reject Heat Speed up reaction / to overcome the activation energy / provide energy to break bonds / because activation energy for the reaction is high (1) Under reflux Prevent escape of reactants / products Or As they may be flammable / harmful / volatile (1) Just to provide energy for the reaction to start Just to increase the yield/make reaction go to completion Question Number 14 (a)(i) Question Number 14 (a)(ii) Question Number 14 (a)(iii)<br />
Mark Mark Mark Acceptable Answers HOCH2CH2N(C2H5)2 Allow OHCH2CH2N(C2H5)2 Allow displayed or skeletal formulae Reject Acceptable Answers Reject Reduction (1) Allow redox Tin / iron / zinc and (conc./dilute) hydrochloric acid (1) Accept correct names or formulae for both alternatives Ignore references to tin as a catalyst Ignore conditions Allow NaBH4 in alkali (Pd catalyst) Addition of NaOH unless clearly after the reduction Hydrogen gas and nickel (catalyst) LiAlH4 Acceptable Answers Reject 100 x 7.77/9.40 = 82.7% Moles of 2-hydroxy benzoic acid = 9.4/138 (1) (= 0.0681) So theoretical yield of aspirin = 0.0681 x 180 (1) = 12.26 g % yield = 100 x 7.77/12.26 = 63.4% (1) Or Moles of 2-hydroxy benzoic acid = 9.4/138 (1) (= 0.0681) Moles of aspirin = 7.77/180 (1) (=0.0432) % yield = 100 x 0.0432/0.0681 = 63.4/63% (1) Correct answer with no working 3 marks Allow 1 max. if Mr values are transposed 108% Question Number 14 (a)(iv) Question Number 14 (a)(v) Question Number 14 (b)(i)<br />
Acceptable Answers Reject Dissolve/add to impure solid in min. volume / amount (1) of hot solvent / water (1) (Filter whilst hot) Allow to cool and filter off product / (re)crystallize and filter off product (1) Wash with cold / small amount of solvent / water (then dry) (1) Just small/little amount of water Named solvents other than waterpenalise once Mark Acceptable Answers It reduces yield as some product remains in solution Allow stated and explained errors due to transfer e.g. left on filter paper Reject Just transfer errors Mark Acceptable Answers Reject Mark Ethanoic acid CH3COCl / (CH3CO)2O / ethanoyl chloride / ethanoic anhydride If both name and formula are given then both must be correct Allow acetyl chloride / acetic anhydride Ignore any additional information Allow displayed formulae Acceptable Answers Reject (Lessen) risk of overdose / as paracetamol is toxic in larger doses/ as paracetamol is harmful in larger doses / reduce risk of taking medication over a longer time period than necessary / reduce risk of addiction Mark Question Number 14 *(b)(ii) Question Number 14 (b)(iii) Question Number 14 (c)(i) Question Number 14 (c)(ii)<br />
Question Number 14 (c)(iii) Acceptable Answers Reject Net forces between paracetamol and water are less than the forces between water and water and / or paracetamol and paracetamol Allow benzene / ring doesnt interact with water Allow benzene ring is hydrophobic / non polar / only forms London forces / cant form hydrogen bonds Just paracetamol / benzene ring is large / steric hindrance Mark<br />

Question 13 14 15 16 17

About us | Need Help? | Feedback

Proudly powered by WordPress | Theme: Sydney by aThemes.